Characterisation of selected South African clays for defluoridation of natural waters

Abstract

In large parts of South Africa groundwater contains excessive fluoride. In many such areas fluorosis is a serious problem among the local population. One way of solving the problem is to use simple house-based deflouridation systems using suitable clays, processed in various ways, as adsorbents. No information on the fluoride removal capacity of South African clays and soils is currently available. This study assesses the fluoride adsorption characteristics of clays selected from areas, such as the western Bushveld, where high fluoride concentrations in groundwater is a problem. Bauxitic clays were found to have the best overall potential as fluoride adsorbents. South African bauxite deposits, however, are not only low grade but are also to be found far from the problem areas in the North-West Province. Simple chemical activation using 1% Na2CO3 solutions and dilute hydrochloric acid could enhance adsorption capacity of certain clay types.